Display-controlling means for cathode ray tubes



Sept. 20, 1955 c. A. LAWS DISPLAY-CONTROLLING MEANS FOR CATHODE RAY TUBES Filed May 17, 1954 is Z #1 w; N6 M Q United States Patent DISPLAY-CONTROLLING MEANS FOR CATHODE RAY TUBES Cecil Alfred Laws, St. Albans, England, assignor to Elliott Brothers (London) Limited, London, England, a company of Great Britain Application May 17, 1954, Serial No. 430,297 Claims priority, application Great Britain May 18, 1953 7 Claims. (Cl. 315-9) This invention relates to display-controlling meansfor cathode ray tubes and is more particularly concerned with such means of the kind (hereinafter referred to as the kind specified) which cause the display of predetermined patterns or symbols on the fluorescent screen of a cathode ray tube by simultaneously varying the displacement potentials respectively applied to the X plates and the Y plates of the cathode ray tube so that the X plate potential has a Waveform representing the horizontal component of the required displacement of the electron beam and the Y plate potential has a waveform representing the vertical component of this displacement.

It is the object of the present invention to provide improved means of this kind which shall be simpler to construct and maintain than those hitherto available.

It is known that an electrical output having a Waveform representing a given contour may be generated with the aid of a photo-electric or photo-multiplier cell, a cathode ray tube and a displaceable opaque mask of the given contour, the mask being moved between the cell and the C. R. T. in the general direction in which the contour extends (say horizontally), the output from the cell, after amplification in a D. C. amplifier, being applied as a deflecting potential to those plates of the C. R. T. (say the Y plates) which control the deflection of the electron beam in a direction normal to the direction of movement of the mask, and the sign of the output being such as to deflect the beam towards the opaque area of the mask, the beam normally being biased away from this area by a steady potential applied to said plates of the C. R. T. The output from the amplifier has the waveform of the contour and as the effective output impedance of the amplifier is low, due to the high loop gain employed in such a system, this output may be fed directly intosignal leads. Such a system will be referred to below as a contour waveform generator.

According to this invention display-controlling means of the kind specified comprises two contour waveform generators having their outputs respectively applied to the X and Y plates of a cathode ray tube intended to display the predetermined patterns or symbols and having their displaceable masks arranged each to carry a plurality of contours arranged in sequence on the circumference of a circle, the contours of the one mask which represent the horizontal components of the required deflections of the electron beam being disposed angularly about the centre of the respective circle in relation to the C. R. T. of the corresponding contour waveform generator in an exactly similar manner to that in which the respective contours of the other mask representing the vertical components of said deflections are located angularly about the centre of the other circle in relation to the C. R. T. of the other contour waveform generator, and means for rotating the two masks in synchronism about the centres of the respective circles in order to traverse the contours sequentially through the contour waveform generators.

The masks may conveniently be constructed as trans- 2,718,608 Patented Sept. 20, 1955 parent discs having areas thereof rendered opaque to define the required contours and these discs may be mounted on a common shaft adapted to be rotated by an electric motor or other means.

It will be appreciated that all the patterns or symbols represented by the two sequential sets of contours will be painted on the screen of the displaying C. R. T., by the electron beam of the latter, in succession as the masks execute a complete rotation. Moreover, without other provision being made, the patterns or symbols will all be superimposed. Since it is necessary, in general, that the patterns or symbols may be seen separately, a different set of predetermined X and Y displacement potentials is introduced with the component waveforms of each pattern or symbol so that the patterns or symbols will appear at different locations on the screen. This may be effected, for example, by providing additional contours onseparate trackson each disc so that they constitute the masks for further contour Waveform generators, the outputs from these generators being employed to operate electric or electro-mechanical switches in synchronism with the production of the individual pattern waveforms and the switches being arranged to apply the necessary predetermined displacement potentials to the plates of the C. R. T. Thus patterns or symbols may be produced at predetermined locations on the face of the C. R. T. so that these locations may be identified by the associated pattern or symbol for ease of reference. This is advantageously of application to radar screens where it is desired to identify an area being scanned by a symbol.

It should be noted, however, that a convenient waveform track for switching purposes may, be constituted of a simple on-off type of pattern, e. g. opaque areas alternating with transparent areas, so that a contour follower C. R. T. will not be required and may be replaced by a single lamp.

It will be understood that similar means may be provided for controlling the waveform of the brightening pulse for the displaying C. R. T.

The general arrangement of one form of display-controlling means according to this invention is illustrated somewhat diagrammatically in the accompanying drawings, wherein: s

Fig. 1 is a face view of a displaceable mask, and

Fig. 2 is a side view of a pair of contour waveform generators each employing a mask of the character of that shown in Fig. 1.

As can be seen from Fig. 1, the displaceable mask 1 is constructed as a disc of transparent material which carries a plurality of contours 2, 3, 4 defined by the boundaries of opaque areas on the disc and arranged in sequence on the circumference of a circle concentric with the disc. The contours of the mask 1 represent the horizontal components of the required deflections of the electron beam of the main or displaying C. R. T. (not shown) and those of a similar mask 1a (Fig. 2) represent the vertical components of these deflections. The two masks 1, 1a are mounted on a common shaft 10, see Fig. 2, arranged to be driven by an electric motor 11, the corresponding contours of the two masks being correctly oriented in relation to each other so that when a given contour of the mask 1 is passing through a scanning location the respective contour of the mask 1a will also be passing through a similar scanning location. At each of these scanning locations are arranged the elements which make up, together with the appropriate mask, a contour waveform generator, i. e. a cathode ray tube 12 (or 12a), a photo-electric cell 13 (or 13a), and an' amplifier 14 (or 14a).

The amplifier output from the photo-electric cell 13 associated with the mask 1 is utilised to supply or control the displacement potential applied to the X plates 18 of in most cases,

the main C. R. T. 19, Whereas the amplified output from the photo-electric cell 13a associated with the mask 1a is utilised to supply or control the displacement potential applied to the V plates 20 of the main C. R. T. 19 to display a predetermined pattern or configuration on the face thereof in accordance with the component patterns being scanned on the two masks 1 and 1a. Thispattern is a function of the angular displacement of the shaft 10. It will be appreciated that the pattern or configuration displayed on the main C. R. T. 19 may therefore be a function and indication of the angular position of the h f 0,-

The disc or mask 1a also carries a waveform track 15 for switching purposes which co-operates with a lamp 16 and a further photo-electric cell 17, the output from the latter being employed to operate suitable switches as se or h o e W at I l im. is:

1. Display controlling means of the kind specified comprising two contour waveform generators of the character referred to, having their outputs respectively applied to the X and Y plates of a cathode ray tube intended to display the predetermined patterns or symbols and having their displaceable masks arranged each to carry a plurality of contours arranged in sequence on the circumference of a circle, the contours of the one mask which represent the horizontal components of the required deflections of the electron beam being disposed angularly about the centre of the respective circle in relation to the cathode ray tube of the corresponding contour waveform generator in an exactly similar manner to that in which the respective contours of the other mask representing the vertical components of said deflections are located angularly about the centre of the other circle in relation to the cathode ray tube of the other contour waveform generator, and means for rotating the two masks in synchronism about the centres of the respective circles in order to traverse the contours sequentially through the contour waveform generators.

2. Display controlling means according to claim 1 wherein the masks are constructed as transparent discs having areas thereof rendered opaque to define the required contours.

3. Display controlling means according to claim 2 wherein the discs are mounted .on a common shaft adapted to be rotated by an electric motor.

4. Display controlling means according to claim 2 wherein means is provided for introducing into the component waveforms of each pattern or symbol a different combination of predetermined X and Y displacement potentials so that each pattern or symbol will appear at different locations on the screen of the cathode ray tube.

5. Display controlling means according to claim 4 wherein said means includes additional contours on a separate track on at least one of the discs to constitute the mask for a further contour waveform generator.

6. Display controlling means according to claim 5 including switch means operable by the output from said further contour waveforms generator in synchronism with the individual pattern waveforms to apply the necessary predetermined displacement potential to at least one set of the displacement plates of the cathode ray tube.

7. Means for controlling the display of a predetermined pattern on the screen of a main cathode ray tube having X and Y deflection plates comprising two contour waveform generators each including a photo-electric cell, a cathode ray tube and a displaceable mask carrying a plurality of contours arranged in sequence on the circumference of a circle, the contours of one mask representing the horizontal components of the required deflections of the electron beam of the main cathode ray tube to produce said pattern and being disposed angularly about the centre of the respective circle in relation to the cathode ray tube of the corresponding contour waveform generator in an exactly similar manner to that in which the respective contours of the other mask representing the vertical components of said deflections are located angularly about the centre of the other circle in relation to the cathode ray tube of the other contour waveform generator, means for moving each mask in synchronism with the other between the associated cell and cathode ray tube to traverse the contours sequentially between said cell and said cathode ray tube, means for scanning the contours carried by each mask by a light beam generated by the associated cathode ray tube, said light beam being arranged to follow said contours to produce an electric output having a waveform which is a function of the shape of the contour being scanned, means for applying the electric output from one of said contour waveform generators to the X plates of said main cathode ray tube and means for applying the electric output from the other of said contour Waveform generators to the Y plates of said main cathode ray tube to produce said predetermined pattern on the screen of the latter.

References Cited in the file of this patent UNITED STATES PATENTS 1,398,552 Norton Apr. 16, 1946 2,462,263 Haynes Feb. 22, 1949 2,528,020 Sunstein Oct. 31, 1950 2,540,943 Hales Feb. 6, 1951 2,681,424 Hergenrother June 15, 1954 

